Study links caffeine with pregnancy loss

People who drink more than a little caffeine when they're trying for a pregnancy are more likely to lose that pregnancy early on, the study found. And that goes equally for men or women.

When either men or women drank three or more cups a day of caffeinated drinks — sodas, energy drinks or coffee — the woman was nearly twice as likely to lose that pregnancy early on.

It's one of the most detailed studies yet to look at something that has been noted for a while now — that high caffeine intake seems to be linked with pregnancy loss.

And it's one of the first to show that what men eat or drink can affect fertility.

"There's something about drinking caffeinated beverages that is associated with pregnancy loss," said Germaine Buck Louis of the National Institute of Child Health and Human Development, who led the study.

But women who took multivitamins before they got pregnant and early in pregnancy were 50 percent less likely to miscarry, the study found.

Their findings come out of an intensive study of 344 couples in Texas and Michigan who have agreed to be watched as they try to conceive. They wrote down every caffeinated drink they had, every serving of fish, every alcoholic drink, were weighed regularly, gave urine, blood, saliva and semen samples and the women took regular pregnancy tests.

The idea: to see what might affect a woman's ability to get pregnant and stay pregnant.

There will be answers later to questions about mercury from fish and chemicals such as pesticides. This study looks at caffeine.

"Our findings provide useful information for couples who are planning a pregnancy and who would like to minimize their risk for early pregnancy loss," Louis said.

Of the 344 pregnancies, 28 percent of them ended in miscarriage: 98 in total, the team reports int he journal Fertility and Sterility.

Women who were over 35 had twice the risk of an early miscarriage as younger women - that's long been known.

But drinking three or more caffeinated beverages a day raised the risk of early pregnancy loss by 74 percent. That held whether it was before conception or afterwards.

"Our findings also indicate that the male partner matters, too," Louis said. "Male preconception consumption of caffeinated beverages was just as strongly associated with pregnancy loss as females'."

The study did not look for differences among various caffeinated drinks, but lumped coffee and tea together with sodas and energy drinks.

RELATED: Risk factors for complications during pregnancy

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Risk factors for complications during pregnancy

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Study links caffeine with pregnancy loss

Advanced maternal age

Pregnancy risks are higher for mothers age 35 and older.

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Lifestyle choices

Smoking cigarettes, drinking alcohol and using illegal drugs can put a pregnancy at risk.

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Medical history

A prior C-section, low birth weight baby or preterm birth — birth before 37 weeks of pregnancy — might increase the risk in subsequent pregnancies. Other risk factors include a family history of genetic conditions, a history of pregnancy loss or the death of a baby shortly after birth.

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Underlying conditions

Chronic conditions — such as diabetes, high blood pressure and epilepsy — increase pregnancy risks. A blood condition, such as anemia, an infection or an underlying mental health condition also can increase pregnancy risks.

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Pregnancy complications

Various complications that develop during pregnancy pose risks, such as problems with the uterus, cervix or placenta. Other concerns might include too much amniotic fluid (polyhydramnios) or low amniotic fluid (oligohydramnios), restricted fetal growth, or Rh (rhesus) sensitization — a potentially serious condition that can occur when your blood group is Rh negative and your baby's blood group is Rh positive.

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Multiple pregnancy

Pregnancy risks are higher for women carrying twins or higher order multiples.

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Louis said there has been a debate about whether caffeine causes miscarriages, or whether women who instinctively stop drinking caffeine early in pregnancy have a healthier pregnancy to start with. Because her study looked at caffeine consumption right before pregnancy, before a woman could develop an aversion to the stuff, it supports the idea that it's the caffeine itself causing the miscarriage, Louis said.

The good news is that taking a multivitamin really helps.

'We were really surprised at how strong the reduction in risk was," Louis said.

"We think this is really good news. We know that vitamins protect against a lot of other adverse pregnancy outcomes."

Dr. Rebecca Starck, who chairs the gynecology department at the Cleveland Clinic, said the study cannot show cause and effect.

"The main message of the study is that it's important to seek preconception counseling," said Starck, who was not involved in the research.

"Anybody of childbearing age who is contemplating pregnancy should maintain a healthy diet and healthy lifestyle and someone who is going to conceive should be aware of effects of lifestyle on the offspring."

Starck noted that miscarriage is common and the study confirmed that: 25 percent to 30 percent of pregnancies end in miscarriage.

The study did not ask people what else they ate or drank besides alcohol and caffeinated beverages. Louis says it will be important to ask people about diet drinks, for instance. She said the study cannot answer questions about whether people who eat healthier diets — with more fruits and vegetables and less salt and fat — are better able to conceive and keep a pregnancy.

As with all medical and scientific studies, each one builds on the other, and it will take larger studies to answer some of the questions.